1. Field of the Invention
The present invention relates to a surface hardening method for resins used, for example, as an optical disk substrate, magnetic disk or magneto-optical disk substrate, a surface hardened resin, a production device of the surface hardened resin, and an information carrier-use resin disk substrate used therein.
2. Description of the Related Art
Conventionally, aluminum, glass, etc. have been used for an optical disk substrate, magnetic disk or magneto-optical disk substrate because such materials are easily processed to have rigidity, smoothness and so on. In recent years, however, a resin substrate has been proposed because it is inexpensive and allows pits and grooves to be formed easily by the injection molding.
Although such a resin disk substrate is inexpensively producible, it is easily deformed by external forces. Thus, it is necessary to perform a surface hardening treatment for the resin disk substrate.
However, conventionally, in order to reform the physical properties of the surface of plastics, ion implantation is simply performed by implanting ions at a certain energy level (between several tens KeV to several MeV).
A method of hardening only the vicinity of the surface to a sufficient surface hardness has not been established at present.
Then, an objective of the present invention is to provide a surface hardening method for resins and a surface hardened resin, which are capable of reforming the surface of an object to be treated under low energy in a short time, a production device of the surface hardened resin, and an information carrier-use resin disk substrate.
The present inventors noted recently-studied techniques of implanting ions into plastic materials. For example, see Proceedings at the 45th Meeting of the Affiliated Association of Applied Physics Society, Riken, Iwaki, No. 2, p. 687 29-p-ZB-10; and Thin Film Tripology (Tokyo University Publishing), p.128, S. hibi, The 18th symp. on ion implantation and submicron fabrication, Rikagaku Kenkyusho, 1987, 81. These techniques have been studied and the application of such techniques have been directed to a disk-shaped information carrier. As a result, the inventors found that it is possible to reform the surfaces of resins and obtain disk-shaped substrates with surfaces which do not have cracks or plastic deformation, by implanting ions such as carbon ions, argon ions, nitrogen ions, silicon ions, etc. into the entire surface of substrates made of resins, such as acrylic-based resins, polyethylene terephthalate, polycarbonate, amorphous polyolefine, and high-density polyethylene, at least on a side which supports an information recording layer.
Moreover, the present invention relates to a surface hardening method for resins, for hardening the surface of a resin to be treated, by performing alternately ion implantation and physical film deposition under a different condition from that for the ion implantation on the resin (hereinafter referred to as the xe2x80x9chardening method 1xe2x80x9d of the present invention).
In addition, the present invention relates to a surface hardening method for resin, for hardening the surface of a resin to be treated, by simultaneously performing ion implantation and physical film deposition on the resin (hereinafter referred to as the xe2x80x9chardening method 2xe2x80x9d of the present invention).
Furthermore, the present invention relates to a surface hardening method for resins, for hardening the surface of a resin to be treated, by performing ion implantation on the resin under the influence of a bias electric field (hereinafter referred to as the xe2x80x9chardening method 3xe2x80x9d of the present invention).
According to the hardening methods 1, 2 and 3 of the present invention, since ion implantation and physical film deposition under a different condition are performed alternately or simultaneously, or ion implantation is performed under the influence of a bias electric field, a thin or shallow ion-implanted layer and a physically deposited film are formed on the surface of the resin alternately or simultaneously under low energy, and it is possible to harden the surface of the resin without producing a boundary face in substantially the same manner as in the case where the physically deposited film is formed on the ion-implanted layer. Moreover, if a bias electric field is applied, the implantation ions are accelerated and the implantation efficiency is improved, thereby increasing the hardening rate. Consequently, for example, if the surface of the resin is reformed to a material rich in the DLC (diamond like carbon) structure and if the resultant material is applied to a disk substrate, it is possible to fabricate a good-quality product having no cracks or the like in a short time, thereby improving the productivity.
Additionally, the present invention relates to a surface hardened resin formed by layering an ion-implanted resin of high hardness and a film layer of high hardness (hereinafter referred to as the xe2x80x9chardened resinxe2x80x9d of the present invention).
Since the hardened resin of the present invention is a hardened resin produced by the above-mentioned surface hardening methods, it is possible to provide a satisfactory surface hardened resin having the same effects as the above-mentioned hardening methods.
Moreover, the present invention relates to a production device of a surface hardened resin (hereinafter referred to as the xe2x80x9cReproduction device 1xe2x80x9d of the present invention) including an ion implanting means and a physical film depositing means operated under a different condition from that for the ion implanting means, the ion implanting means and the physical film depositing means being disposed to face a resin to be treated (both the means can be achieved by the same device).
Besides, the present invention relates to a production device of a surface hardened resin (hereinafter referred to as the xe2x80x9cproduction device 2xe2x80x9d of the present invention), which is designed to perform the ion implantation and the physical film deposition simultaneously on a resin to be treated.
Furthermore, the present invention relates to a production device of a surface hardened resin (hereinafter referred to as the xe2x80x9cproduction device 3xe2x80x9d of the present invention), which is designed to perform the ion implantation on a resin to be treated under the influence of a bias electric field.
With the production devices 1, 2 and 3 of the present invention, it is possible to provide a production device of good reproducibility according to the above-mentioned production methods.
Other objects and advantages of the invention will become apparent upon reading the following detailed description and a appended claims, and upon reference to the accompanying drawings.